1. Field of the Invention
The present invention relates to a bearing apparatus for a vehicle, and more particularly, to a bearing apparatus for a vehicle for rotatably supporting wheels of an automobile.
2. Description of the Related Art
Referring to FIG. 7, a conventional bearing apparatus for a vehicle will be explained. The term xe2x80x9cvehicle-inner sidexe2x80x9d herein means right side in the drawings, and the term xe2x80x9cvehicle-outer sidexe2x80x9d means left side in the drawings.
This bearing apparatus includes a hub wheel 1, a double row type rolling bearing 2 and a constant velocity joint 3. The hub wheel 1 has a hollow hole in its axial direction. An outer ring 31 of the constant velocity joint 3 includes a cup-like cylindrical portion (outer ring cylindrical portion) 35, and a shaft (outer ring shaft) 36 continuously formed on this in the direction of the vehicle-outer side. The outer ring shaft 36 is spline fitted to the hollow hole of the hub wheel 1. A vehicle-inner side end of the hub wheel 1 is bent radially outward, thereby the end is caulked against an end face of an inner ring 25 of the rolling bearing 2 on the vehicle-inner side. The caulked vehicle-inner side end of the hub wheel 1 is defined as a caulked portion 14. With this caulk, a necessary pre-load is applied to the rolling bearing 2, so that rolling characteristics of the rolling bearing 2 are secured.
On the other hand, a nut 10 having a head whose outer diameter is greater than the hollow hole of the hub wheel 1 is threadedly engaged around a vehicle-outer side end of the outer ring shaft 36. The hub wheel 1 is sandwiched by the threadedly engaged nut 10 and the outer ring cylindrical portion 35 of the constant velocity joint 3 between the vehicle-outer side and the caulked portion 14, which is the vehicle-inner side, from both of the opposite sides in the axial direction. With this construction, the outer ring 31 of the constant velocity joint 3 is coupled to the hub wheel 1.
In the case of such a coupling construction, if a fastening force of the nut 10 is weak, the outer ring 31 of the constant velocity joint 3 cannot be strongly coupled to the hub wheel 1 and thus, the fastening force of the nut 10 must be strong enough for the coupling mentioned above.
Therefore, the fastening force of the nut 10 tends to be excessively strong. In such a case, the caulked portion 14 of the hub wheel 1 is strongly pushed toward the vehicle-outer side from the outer ring 31 of the constant velocity joint 3 and compressed and deformed, and redundant load is prone to be applied to the rolling bearing 2.
In such a case, the redundant load against the rolling bearing 2 caused by the fastening of the nut 10 is applied to the rolling bearing 2 as pre-load in addition to a pre-load set by the caulking of the vehicle-inner side end of the constant velocity joint 3. Thus, the pre-load cannot be maintained properly, and there is a tendency that the rolling characteristics of the bearing 2 are deteriorated.
For the above reasons, in the case of the conventional bearing apparatus, the coupling operation of the outer ring 31 of the constant velocity joint 3 to the hub wheel 1 is required to be carried out under a predetermined condition, and this operation is ineffective and troublesome.
Therefore, it is a main object of the present invention to provide a bearing apparatus for a vehicle capable of coupling a constant velocity joint to a hub wheel with easy and effective operation, while properly keeping the pre-load to a rolling bearing.
Other objects, features and advantages of the present invention will be apparent from the following description.
A bearing apparatus for a vehicle of the present invention includes a hub wheel having a hollow hole, a rolling bearing mounted to an outer periphery of the hub wheel, a constant velocity joint for connecting an input shaft to the hub wheel such that the input shaft can incline, the constant velocity joint having an outer ring including a cylindrical portion in which an inclination guide element with respect to the input shaft is accommodated and a shaft (outer ring shaft) continuously formed on the cylindrical portion and fitted into the hollow hole of the hub wheel in a state in which the outer ring shaft is prevented from rotating in the hollow hole of the hub wheel in its circumferential direction, a pressing member mounted to the outer ring shaft of the constant velocity joint, and a fixing member whose outer diameter side is fixed to a predetermined position of the hub wheel on a vehicle-outer side and whose inner diameter side is smaller than the hollow hole of the hub wheel, wherein the fixing member is sandwiched between the pressing member and a vehicle-outer side end face of the outer ring shaft in the axial direction so that the outer ring of the constant velocity joint is coupled to the hub wheel.
The fixing member fixed to the hub wheel is sandwiched between the outer ring shaft of the constant velocity joint and the pressing member in the axial direction and thus, the outer ring of the constant velocity joint is coupled to the hub wheel.
Therefore, in the case of the bearing apparatus for a vehicle of the present invention, a simple coupling operation only for mounting the bolt to the shaft suffices, and a pre-load that has been applied to the rolling bearing is maintained invariably. As a result, a required pre-load may be applied to the rolling bearing only when the hub wheel 1 is caulked and thus, its management becomes easy.
In the present invention, preferably, a vehicle-outer side opening of the hollow hole of the hub wheel is increased in diameter to form a diameter-increased portion. The fixing member is fixed to in the diameter-increased portion of the hub wheel.
In the present invention, preferably, the fixing member is a fixing ring having an outer diameter side fitted and fixed to the diameter-increased portion of the hub wheel by press-fitting, a vehicle-outer side end of the outer ring shaft of the constant velocity joint has a screw hole, the pressing member is a bolt threadedly engaged in the screw hole, the fixing ring is sandwiched between the vehicle-outer side end face of the outer ring shaft and an inner end face of a head of the bolt threadedly engaged in the screw hole in its axial direction in a state in which the fixing ring is positioned at least in its axial direction.
In the present invention, preferably, the fixing member is fixed to the diameter-increased portion of the hub wheel by press-fitting. This press-fit force is set greater than an axial load applied to the outer ring of the constant velocity joint in a direction of the vehicle-outer side.